Yum! Spaghetti squash is a staple in my house, I have it at least once a week and cook it numerous ways.
Once cooked, you should use it within 3 days, but I believe you can store them in a dark, cool place for a couple of weeks. I've also had good results freezing it after it's been cooked and shredded.
If you enjoy it sweetened, try it with a little Smart Balance spread and a drizzle of SF maple syrup.